As a related-art buckle which detachably connects two objects that are to be connected, Patent Document 1 discloses a buckle which can be locked in the state in which a male member and a female member are connected to each other. The related-art buckle includes a male member having a pair of engaging portions, a female member having an engaged portion with which the engaging portions of the male member are engaged so as to connect the male and female members to each other, and a lock member which is provided in the female member. The lock member is positioned between the engaging portions of the male member, and selectively prevents or allows the disengaging operation of the engaging portions. In the male member, the engaging portions each having an operation portion are positioned at sides. The female member has operation openings in a pair of sides through which the operation portions positioned at the sides are exposed. As for the connection and disconnection of the buckle, the engaging portions are disengaged from the engaged portion when the operation portion of the male member is pressed in the connected state. The lock member has an elliptical shape, and is configured such that a position where the engaging portions of the male member are allowed to swing to a disengaging position and a position where the engaging portions of the male member are prevented from swinging to the disengaging position are selectable depending on the direction of the long axis of the ellipse.
Patent Document 1: U.S. Pat. No. 7,181,936
The buckle disclosed in Patent Document 1 has problems in that the lock member is attached to the female member as a separate part and that there is a great number of parts. In addition, since the lock member is provided as a separate member, the fabrication and assembly processes of the buckle are complicated, and the fabrication cost of the buckle is expensive. Furthermore, since the lock member is accommodated inside the female member, it is difficult to reduce the thickness of the female member. In a variety of situations of use, the buckle protruding from the surface of a member to which the buckle is attached frequently became an obstacle and the appearance was not undesirable.